The present invention relates to methods and arrangements in a mobile 3rd generation communication system and user equipments intended for usage in such systems. It relates in particular to situations when certain services, e.g. related to emergency calls, in the UTRAN are not available while the user equipment could perform this service also over a backup network, e.g. a GSM-network, which it can access.
The technology disclosed herein relates to the radio network part (UTRAN) of a 3rd generation communication system, e.g. a WCDMA-system, to which the following will refer to as an example, and addresses in particular problems that may arise when certain services, which the network is supposed to offer, are unavailable, e.g. due to faults in one of the units or links of said communication system or due to temporary congestions in said communication system.
Present 3rd generation communication systems, as standardised by the 3rd Generation Partnership Project (3GPP), do not fully support to use another communication system, e.g. a GSM-system, as a backup system for services that are temporarily unavailable. Vice versa, there is presently no full support to use the UTRAN as a backup system, e.g. of a GSM-system, which is only used for certain services. Instead, a user equipment must stay in the communication system, which it presently is associated to, although a required service is presently not available or the user equipment is forced to move entirely to the backup communication system, although certain services that are needed by the user equipment would still be available in the disturbed system.